From Short-Term Erosion to Long-Term Landforms: Linking Different Coastal Erosion Models to Marine Terrace Formation

The combined record of past sea levels and crustal deformation can be found in the landscapes of tectonically active coastlines. Marine terraces, sea cliffs, or intertidal platforms all reflect the work of multiple geomorphic processes sculpting the coast. Researchers have investigated the key erosional mechanisms responsible for shaping the coasts. Field observations suggest that platform formation is driven by three primary processes: (1) mechanical erosion from the kinetic energy of marine waves, (2) physical or chemical weathering driven by wetting-drying cycles, and (3) biochemical weathering, which may amplify or even sometimes dominate the other two processes. However, determining the dominant process remains challenging, as each mechanism is interacting with other processes, making it is hard to disentangle their relative contribution. Numerical models for coastal evolution exist but we are not able to properly evaluate their accuracy, or to convincingly simulate the respective roles of different processes over 100s of kyr.

In this study, we compare and assess the outputs of models that emphasize different processes by simulating the shoreline evolution trajectories under identical (or varying) wave conditions and sea level scenarios. The results reveal that the shape of coastal topography, including intertidal platform, varies significantly depending on the dominant process or assumptions, such as the rate of debris removal from failed cliffs. Notably, these differences become more pronounced when considering the direction of sea level change. Additionally, we build a framework that enables the simulation of process combinations by selectively activating or deactivating specific modules within the system. By systematically comparing models and their combinations, we aim to develop a comprehensive framework for coastal erosion that can be adapted to specific sites and conditions.

Looking ahead, we seek to link these distinct platform development trends to long-term coastal morphological features, such as marine terraces. Over geological timescales characterized by glacial sea level fluctuations, prolonged platform formation may produce distinct marine terraces. Understanding these trends in coastal erosion can provide valuable insights into the generation and preservation of coastal geomorphology.